Weird thread shape after trying to offset faces in threads to add clearance

[erpijyt1307]

Hello,

I tried to make a custom thread using coil feature. After trying to offset the faces in the threads to add clearance, Fusion 360 is making weird modeled threads that are getting crooked.

Attached are the screenshots. Any insights to fixing is appreciated.

[wmhazzard]

It may be a graphics issue, try a section analysis to see if it is really there. If it is, attach an f3d file of your model. 

[jeff_strater]

agree with @wmhazzard here - this looks like a graphics issue.  However, section analysis might not help, since those are done with graphics, as well.  You can try the "Display Detail Control", and choosing different "Fixed" settings, to see if that helps.

[erpijyt1307]

Hello William,

I don't think its a graphics problem. Exporting the file as mesh shows the same crooked geometry. I am attaching the f3d file.

Jeff, 

Tried out your suggestion, weirder things are happening to the thread. Attaching the f3d file for convenience. 

[jeff_strater]

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@erpijyt1307 wrote:

Hello William,

I don't think its a graphics problem. Exporting the file as mesh shows the same crooked geometry. I am attaching the f3d file.

Jeff, 

Tried out your suggestion, weirder things are happening to the thread. Attaching the f3d file for convenience. 

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Actually, export as mesh uses the graphics facets, so the fact that shows the same geometry is not surprising, and also does not prove that it is not graphics.

Thanks for sharing the design.  Can you explain a bit more about the "weirder things"?  What I see in that thread is what I expect, even after the offset faces features

[erpijyt1307]

Yes, it might be a graphics issue, won't know much until I get it 3d printed for myself. Attached a few pictures for your reference. Putting the f3d file in the autodesk online viewer also shows the same as in Fusion 360 application

[wmhazzard]

I see the irregular faces on the thread on your model but I am unable to reproduce it on a new model on my computer. 

[erpijyt1307]

Thats unfortunate. No idea what's really the case here. Tried the coil feature independently in a new file without making any other bodies. The result is the same. Since the part is already small, I hope the irregularities doesn't show much in 3d printing

[jeff_strater]

Because the mesh export uses the same faceting as the graphics system uses, you will likely see the same geometry in an STL export, unless you set the accuracy pretty high.  Though this does not fix the problem, you can see in the screencast that changing the display detail control does affect those faces.  To me, that shows that this is a faceting problem, not a geometry problem.  I realize that doesn't help you, but it is important to us, since it tells us where the fix needs to be.

[wmhazzard · Accepted solution]

It looks like the smaller the thread, the worse the distortion is when offsetting the face. I think the best way around this would be to alter the section size of the coil and not to offset the face. 

[erpijyt1307]

Hi Jeff, Yes that's the exact problem I am facing. 

Hi William, Thanks for the heads up for the simple solution. Wasn't able to figure out what to do for this issue. This resolved my issue. 

[jeff_strater]

This has been confirmed as a faceting issue, logged as ASM-10106.  Thanks for sharing this model with us.  I had not seen that particular problem before...